Various types of wireless communication systems may be used to provide radio communication between central base station (or access point) and one or more remote or mobile units. What they have in common is a base station, that is typically one or more computer controlled radio transceivers interconnected to a land-based network such as a Public Switched Telephone Network (PSTN) in the case of voice communication, or a Wireless Local Area Network (WLAN) for data communications. The base station includes an antenna apparatus for sending forward link radio frequency signals to the mobile units. The base station antenna is also responsible for receiving reverse link radio frequency signals transmitted from each mobile unit. Each mobile unit also contains an antenna apparatus for the reception of the forward link signals and for transmission of the reverse link signals. A typical mobile unit is a digital cellular telephone handset or a wireless modem or wireless adapter coupled to a personal computer.
The most common type of antenna used to transmit and receive signals at a mobile unit is a omni-directional monopole antenna. This type of antenna consists of a single wire or antenna element that is coupled to a transceiver within the subscriber unit. The transceiver receives reverse link signals to be transmitted from circuitry within the subscriber unit and modulates the signals onto the antenna element at a specified frequency assigned to that subscriber unit. Forward link signals received by the antenna element at a specified frequency are demodulated by the transceiver and supplied to processing circuitry within the subscriber unit. In many types of wireless cellular systems, multiple mobile subscriber units may transmit and receive signals on the same frequency and use coding algorithms to detect signaling information intended for individual subscriber units on a per unit basis.
The transmitted signal sent from a monopole antenna is omnidirectional in nature. That is, the signal is sent with the same signal strength in all directions in a generally horizontal plane. Reception of signals with a monopole antenna element is likewise omnidirectional. A monopole antenna does not differentiate in its ability to detect a signal on one direction versus detection of the same or a different signal coming from another direction.